1. Field of the Invention
The invention relates to a conversion device, and more particularly to a power conversion device with digitally controlled comparator.
2. Description of the Related Art
Electronic devices usually consist of a plurality of different electronic elements, and each electronic element requires different operating voltages. Thus, a power conversion device is used to generate a stable voltage with different voltage levels for those semiconductor devices. Such as, a DC-to DC conversion module is a semiconductor switch device for converting a DC voltage to a certain level and supplies the converted DC voltage to a load.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a conventional DC-DC conversion device. As shown in FIG. 1, the DC-DC converter with analog comparator comprises a control signal generator 12, a conversion module 14, resistors, R1 and R2, and a comparator 16. The control signal generator 12 receives a clock signal SCLK and a feedback signal SCOM form the comparator 16, and then transforms those input signals into control signal SC by a series of logic operations. The control signal SC controls the conversion module 14 to convert an input voltage VDD to generate an output voltage VOUT. The divider resistors R1 and R2 divide the output voltage VOUT to generate a divided voltage VDIV. The comparator 16 compares the divided voltage VDIV and a reference voltage VREF and then delivers feedback signal SCOM to control signal generator 12. The control signal generator 12 regenerates the control signal SC according to the change of the feedback signal SCOM. The conversion module 14 changes the voltage level of the output voltage VOUT by the control signal SC.
However, the response of the control signal SC is very fast with the changing of feedback signal SCOM. Thus, when an abnormal pulse occurs in feedback signal SCOM due to noises (such as a clock signal couples to VDIV through parasitic capacitance), the output voltage VOUT of the conversion module 14 of the power conversion device 10 may not keep stable in the vicinity of a predetermined voltage level. Thus, the electronic devices connected to the DC-DC conversion device 10 doesn't work properly. Moreover, with a regulation mechanism applied to the DC-DC converter output, the output would have ripple voltage at the regulation level. The quantity of the output ripple depends on the feedback signal SCOM of the comparator 16 and the loading of the electronic devices coupled to the power conversion device 10. Thus, large ripple voltage can be regarded as an interference to the electronic device connected to DC-DC converter.
Therefore, a DC-DC conversion device can generate accurate output voltage level and limit the variation of ripple voltage is desired